Doherty amplifier and amplification circuit

Abstract

In a case where the power of a signal to be amplified is greater than or equal to a threshold value, a signal distributor (2) outputs one of signals to a carrier amplifier (6), outputs another signal, a phase of which is 90 degrees behind that of the one of the signals, to a peak amplifier (8), and adjusts a phase shift amount of a signal shifted by a phase shifter (7) depending on the frequency of the signal to be amplified. In a case where the power of the signal to be amplified is less than the threshold value, the signal distributor (2) outputs the one of the signals to the carrier amplifier (6) without outputting the other signal to the peak amplifier (8).

1 . A Doherty amplifier comprising:
 a signal distributor dividing a signal to be amplified to signals and distributing the signals;   a carrier amplifier amplifying one of the signals distributed by the signal distributor;   a phase shifter adjusting a phase of the one of the signals amplified by the carrier amplifier;   a peak amplifier amplifying another one of the signals distributed by the signal distributor; and   a signal synthesizer synthesizing the one of the signals, the phase of which is adjusted by the phase shifter, and said another one of the signals amplified by the peak amplifier,   wherein in a case where a power of the signal to be amplified is greater than or equal to a threshold value, the signal distributor outputs the one of the signals to the carrier amplifier, outputs said another one of the signals, a phase of which is 90 degrees behind the phase of the one of the signals, to the peak amplifier, and adjusts a phase shift amount of a signal shifted by the phase shifter depending on a frequency of the signal to be amplified, and   in a case where the power of the signal to be amplified is less than the threshold value, the signal distributor outputs the one of the signals to the carrier amplifier without outputting said another one of the signals to the peak amplifier.   
     
     
         2 . The Doherty amplifier according to  claim 1 , wherein the phase shifter includes:
 an inductive element, one end of which is connected to an output side of the carrier amplifier and another end of which is connected to one of input sides of the signal synthesizer;   a first variable capacitance element, one end of which is connected to the output side of the carrier amplifier and another end of which is grounded; and   a second variable capacitance element, one end of which is connected to the one of the input sides of the signal synthesizer and another end of which is grounded.   
     
     
         3 . The Doherty amplifier according to  claim 1 , wherein the phase shifter includes:
 a first inductive element, one end of which is connected to an output side of the carrier amplifier;   a second inductive element, one end of which is connected to another end of the first inductive element and another end of which is connected to one of input sides of the signal synthesizer; and   a variable capacitance element, one end of which is connected to the other end of the first inductive element and another end of which is grounded.   
     
     
         4 . The Doherty amplifier according to  claim 1 , wherein the phase shifter includes:
 a transmission line, one end of which is connected to an output side of the carrier amplifier and another end of which is connected to one of input sides of the signal synthesizer;   a first variable capacitance element, one end of which is connected to the output side of the carrier amplifier and another end of which is grounded; and   a second variable capacitance element, one end of which is connected to the one of the input sides of the signal synthesizer and another end of which is grounded.   
     
     
         5 . The Doherty amplifier according to  claim 1 , further comprising:
 a first drive amplifier amplifying one of the signals distributed by the signal distributor and outputting the amplified signal to the carrier amplifier; and   a second drive amplifier amplifying another one of the signals distributed by the signal distributor and outputting the amplified signal to the peak amplifier.   
     
     
         6 . An amplification circuit including a plurality of Doherty amplifiers connected to each other in parallel, wherein each of the plurality of Doherty amplifiers includes:
 a signal distributor dividing a signal to be amplified to signals and distributing the signals;   a carrier amplifier amplifying one of the signals distributed by the signal distributor;   a phase shifter adjusting a phase of the one of the signals amplified by the carrier amplifier;   a peak amplifier amplifying another one of the signals distributed by the signal distributor; and   a signal synthesizer synthesizing the one of the signals, the phase of which is adjusted by the phase shifter, and said another one of the signals amplified by the peak amplifier,   wherein in a case where a power of the signal to be amplified is greater than or equal to a threshold value, the signal distributor outputs the one of the signals to the carrier amplifier, outputs said another one of the signals, a phase of which is 90 degrees behind the phase of the one of the signals, to the peak amplifier, and adjusts a phase shift amount of a signal shifted by the phase shifter depending on a frequency of the signal to be amplified, and   in a case where the power of the signal to be amplified is less than the threshold value, the signal distributor outputs the one of the signals to the carrier amplifier without outputting said another one of the signals to the peak amplifier.